“I think it’s going to end up a tragedy,” Coburn said Tuesday, the same day Washington joined Colorado to become the second state legally selling recreational marijuana. “There’s never been a positive study on recreational marijuana. And the connection to further drug use, the connection to depression, connection to lack of motivation -- there’s nothing positive that comes out of it.”

He also warned of dire health consequences, suggesting marijuana may be more likely than tobacco to cause cancer.

"When you smoke a marijuana joint, it’s like smoking 18 cigarettes,” he said. “That’s the amount of carcinogens that you intake.”

He is likely citing a six-year-old study from New Zealand published in the European Respiratory Journal that found smoking one joint is equivalent to the effect that smoking 20 cigarettes has on the lungs. However, later studies, including one from 2012 in the Journal of the American Medical Association, did not detect any damage to pulmonary function -- or the lungs’ ability to take in and release air -- or instances of lung cancer caused by marijuana use.

Mediaite also noted that casual marijuana smokers do not smoke nearly as many joints as tobacco users smoke cigarettes.